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首页> 外文学位 >Investigation of Specimen Geometries for the VECD Model and Calibration of the LVECD Program for Fatigue Cracking Performance of Asphalt Pavements.
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Investigation of Specimen Geometries for the VECD Model and Calibration of the LVECD Program for Fatigue Cracking Performance of Asphalt Pavements.

机译：VECD模型的试样几何形状研究以及LVECD程序对沥青路面疲劳开裂性能的校准。

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摘要

Fatigue cracking is one of the complex distresses that is dependent of pavement structure, asphalt mixture properties and environmental conditions. During the last decades, many asphalt agencies have conducted significant researches to investigate the fatigue cracking characterization. However, fatigue performance is still difficult to predict not only due to models and parameters but also because this phenomenon itself is not well understood.;The key point in fatigue performance prediction is which model to use and how to find the correct parameters for the selected model by using the simplest but the most reliable testing method. The modulus is one of the primary asphalt mixture properties used for the mechanistic performance prediction of asphalt pavements. Dynamic modulus testing is a common method of measuring mixture modulus as a function of loading frequencies and temperatures. Despite the numerous researches that have been carried out to evaluate mixture stiffness, it is still necessary to establish a practical dynamic modulus test method that is compatible with the field cores which are mostly less than a few inches. One of the objectives of this dissertation is to present the results of a ruggedness study of dynamic modulus testing in indirect tension mode to evaluate the factors that are most likely to affect the final results. Specimen thickness, air void content, gauge length, test temperature, and horizontal strain level, that are the critical factors that affect the dynamic modulus of asphalt concrete, were selected for the ruggedness analysis. According to the findings, air void content was found to be a major factor that affects the dynamic modulus values.;To investigate the fatigue life of the pavement, valid cyclic fatigue testing data which truly represents the mixture behavior seems necessary besides the mixture stiffness. With regard to direct tension fatigue testing, one of the common problems that substantially influence the mixture fatigue behavior is the failure at the ends of the asphalt specimens. During testing, it was observed that as more and more material was cut from the top and bottom of the gyratory-compacted specimens, the likelihood of failure in the middle of the specimen greatly increased. Therefore, fabricating shorter test specimens that are cored and cut from taller gyratory-compacted specimens can produce test specimens that have more uniformly distributed air voids such that middle failure occurs within the gauge length of the linear variable differential transformer (LVDT) in direct tension tests. As a part of study, the optimum specimen geometry of 100 mm diameter and 130 mm height was introduced through the experimental testing and numerical simulation.;The Simplified Viscoelastic Continuum Damage (S-VECD) model, a continuum damage mechanics-based model that is known as one of the effective models, has been applied to predict the performance of asphalt concrete mixtures under different loading conditions. Besides, energy-based fatigue failure criterion (GR) has been proved to be able to predict the fatigue life of asphalt concrete mixtures across different modes of loading, temperatures, and strain amplitudes. This dissertation presents the application and calibration of the L&barbelow;ayered V&barbelow;iscoE&barbelow;lastic pavement analysis for C&barbelow;ritical D&barbelow;istresses (LVECD) program which is based on both S-VECD and GR method to evaluate 33 pavement sections from different locations inside the United States, Canada, South Korea, and China. The capability of the LVECD program to capture crack initiation, crack propagation and, the damage in the pavement sections is investigated by comparing the simulation results with the field observations. In this regard, LVECD was found to effectively predict the fatigue cracking propagation in the pavement sections since reasonable agreement was obtained between the program simulations and field observations. Finally, predicted damage-to-field cracking transfer function was developed to correlate the predictive damage to the measured cracking.
机译：疲劳开裂是复杂的问题之一，其取决于路面结构，沥青混合料的性质和环境条件。在过去的几十年中，许多沥青机构进行了重要的研究，以研究疲劳裂纹的表征。但是，疲劳性能仍然难以预测，这不仅是由于模型和参数的原因，而且还因为这种现象本身尚未得到很好的理解。疲劳性能预测的关键是要使用哪种模型以及如何为所选模型找到正确的参数使用最简单但最可靠的测试方法进行建模。模量是用于沥青路面机械性能预测的主要沥青混合料性能之一。动态模量测试是一种测量混合物模量随负载频率和温度变化的常用方法。尽管已经进行了许多研究来评估混合物的刚度，但是仍然有必要建立一种实用的动态模量测试方法，该方法与大多数小于几英寸的励磁磁芯兼容。本文的目的之一是提出一种在间接拉伸模式下进行动态模量测试的耐用性研究结果，以评估最有可能影响最终结果的因素。选择了试样厚度，气隙含量，标距长度，测试温度和水平应变水平，这些是影响沥青混凝土动态模量的关键因素，用于进行坚固性分析。根据调查结果，发现空隙率是影响动态模量值的主要因素。为了研究路面的疲劳寿命，除了混合物刚度之外，似乎还必须有效地代表混合物性能的有效循环疲劳试验数据。对于直接拉伸疲劳试验，实质上影响混合物疲劳行为的常见问题之一是沥青试样端部的破坏。在测试过程中，观察到随着越来越多的材料从旋转压实样品的顶部和底部切下，样品中部发生故障的可能性大大增加。因此，从较高的旋转压实样本中取芯并从中切出较短的样本，可以生产出具有更均匀分布的气孔的样本，从而在直接拉力测试的线性可变差动变压器（LVDT）的标距内发生中间故障。作为研究的一部分，通过实验测试和数值模拟，介绍了直径为100 mm，高度为130 mm的最佳试样几何形状。简化的粘弹性连续体损伤模型（S-VECD）是基于连续体损伤力学的模型，被称为有效模型之一的模型已经用于预测沥青混凝土混合物在不同载荷条件下的性能。此外，已证明基于能量的疲劳破坏准则（GR）能够预测沥青混凝土混合物在不同载荷，温度和应变幅度模式下的疲劳寿命。本论文介绍了基于S-VECD和GR方法的C＆bar; D＆barbelow; istresses（LVECD）程序在L＆bared; Aered V＆barbe; iscoE＆barbe;弹性路面分析中的应用和标定，以评估来自内部不同位置的33个路面截面美国，加拿大，韩国和中国。通过将模拟结果与现场观察结果进行比较，研究了LVECD程序捕获裂纹萌生，裂纹扩展以及路面断面的能力。在这方面，由于在程序模拟和现场观察之间获得了合理的共识，因此发现LVECD可有效预测路面截面中的疲劳裂纹扩展。最后，开发了预测的破坏场裂纹传递函数，以将预测的破坏与测得的裂纹相关联。

著录项

  • 作者

    Norouzi, Amirhossein.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Civil engineering.;Transportation.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 238 p.
  • 总页数 238
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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